Aircraft course measurement method based on RTK receiver and computer vision

Abstract

The invention belongs to the technical field of aircraft state acquisition, and particularly relates to an aircraft course measurement method based on an RTK receiver and computer vision, which is suitable for rapid measurement of aircraft course under an external field condition. According to the method, a horizontally-placed calibrated RTK double-antenna receiver and a binocular vision direction-finding system (an RTK double-visual direction-finding system for short) are adopted, and an included angle between a binocular camera baseline and the north direction is measured by using an RTK double-antenna direction-finding method; meanwhile, measuring an included angle between a projection of a connecting line of two selected datum points on the aircraft in a horizontal plane and a binocular camera base line through a binocular vision system; the course angle of the aircraft is the sum of the two angles. The method is simple in algorithm, the engineering is easy to realize, and the method has large engineering popularization and application space.

Description

Technical Field

[0001] The present invention belongs to the technical field of aircraft state acquisition, and in particular relates to an aircraft heading measurement method based on RTK receiver and computer vision, which can be applied to rapid heading measurement under field conditions. Background Art

[0002] Before launching, an aircraft needs to determine its initial attitude. The pitch and roll angles can be calculated based on the geometric relationship between gravity and the output values ​​of the roll and pitch axis accelerometers. However, the heading angle is not accurate enough for self-alignment of the aircraft's inertial navigation system. Therefore, it is usually necessary to coordinate with the high-precision inertial navigation system on the carrier platform for transfer alignment to measure the aircraft's heading. However, how to evaluate the heading alignment accuracy of the transfer alignment becomes a difficult problem in actual operation. A common solution is to use a photoelectric theodolite to verify the aircraft's heading angle. However, this method is cumbersome and requires a lot of human intervention, making it inefficient in actual use. Therefore, it is necessary to develop a simpler and more automated heading measurement method. Summary of the Invention

[0003] (1) Technical issues to be solved

[0004] The technical problem to be solved by the present invention is: how to design a fast aircraft heading measurement method to evaluate the transfer alignment result during field testing.

[0005] (2) Technical solution

[0006] To solve the above technical problems, the present invention provides an aircraft heading measurement method based on an RTK receiver and computer vision. The method is implemented based on an RTK binocular direction finding system, which includes a horizontally placed and calibrated RTK dual-antenna receiver and a binocular vision direction finding system.

[0007] The method comprises:

[0008] Step 1: Calibrate the RTK binocular direction finding system. When the RTK binocular direction finding system is placed horizontally, the binocular camera baseline and the RTK dual-antenna direction finding baseline coincide, and the binocular camera image plane is perpendicular to the horizontal plane.

[0009] Step 2: Select two reference points on the side of the aircraft, with the line connecting the reference points parallel to the aircraft's roll axis. After the aircraft is ready for launch, place the tripod at a suitable location at the launch point. Adjust the tripod to a horizontal position and place the RTK binocular direction finding system horizontally on the tripod so that both reference points fall within the field of view of the RTK binocular direction finding system's two cameras.

[0010] Step 3: Power on the RTK binocular direction finding system and continuously collect the heading angle output by the RTK dual-antenna receiver. Average the sampling results over a period of time and calculate the average value to obtain the angle between the binocular camera baseline and the north direction, which is recorded as ψ1.

[0011] Step 4: Obtain the positions of the two reference points in the binocular camera image plane, and calculate the coordinate positions of the two reference points in the camera coordinate system based on the binocular vision positioning principle;

[0012] Step 5: Based on the coordinate positions of the two reference points in the camera coordinate system, calculate the angle ψ2 between the projection of the line connecting the two reference points in the horizontal plane and the image plane;

[0013] Step 6: The heading angle of the aircraft can be calculated by combining the angle ψ1 between the binocular camera baseline and the north direction, and the angle ψ2 between the horizontal projection of the line connecting the two reference points on the side of the aircraft and the image plane.

[0014] When the RTK binocular direction finding system is placed horizontally, the binocular camera baseline coincides with the RTK dual-antenna receiver direction finding baseline.

[0015] When the RTK binocular direction finding system is placed horizontally, the image planes of the two cameras are in a vertical plane.

[0016] The distance between the two RTK antennas of the RTK dual-antenna receiver is greater than 2 meters, and the distance between the two cameras is greater than 2 meters.

[0017] Among them, the distance between the two reference points is greater than 2 meters.

[0018] Wherein, the heading angle of the aircraft is ψ 1+ ψ2.

[0019] (3) Beneficial effects

[0020] Compared with the existing technology, the aircraft heading measurement method based on RTK receiver and computer vision proposed in the present invention uses RTK receiver to establish north reference, and measures the angle between the line connecting two reference points on the side of the aircraft and the north direction through binocular vision, thereby realizing the measurement of the aircraft heading angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the on-site layout of the present invention.

[0022] Figure 2 Schematic diagram of the projection of the reference point on the image plane of the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, content, and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below with reference to the accompanying drawings and examples.

[0024] To solve the above technical problems, the present invention provides an aircraft heading measurement method based on an RTK receiver and computer vision. The method is implemented based on an RTK binocular direction finding system, which includes a horizontally placed and calibrated RTK dual-antenna receiver and a binocular vision direction finding system.

[0025] The method comprises:

[0026] Step 1: Calibrate the RTK binocular direction finding system. When the RTK binocular direction finding system is placed horizontally, the binocular camera baseline and the RTK dual-antenna direction finding baseline coincide, and the binocular camera image plane is perpendicular to the horizontal plane.

[0027] Step 2: Select two reference points on the side of the aircraft, with the line connecting the reference points parallel to the aircraft's roll axis. After the aircraft is ready for launch, place the tripod at a suitable location at the launch point. Adjust the tripod to a horizontal position and place the RTK binocular direction finding system horizontally on the tripod so that both reference points fall within the field of view of the RTK binocular direction finding system's two cameras.

[0028] Step 3: Power on the RTK binocular direction finding system and continuously collect the heading angle output by the RTK dual-antenna receiver. Average the sampling results over a period of time and calculate the average value to obtain the angle between the binocular camera baseline and the north direction, which is recorded as ψ1.

[0029] Step 4: Obtain the positions of the two reference points in the binocular camera image plane, and calculate the coordinate positions of the two reference points in the camera coordinate system based on the binocular vision positioning principle;

[0030] Step 5: Based on the coordinate positions of the two reference points in the camera coordinate system, calculate the angle ψ2 between the projection of the line connecting the two reference points in the horizontal plane and the image plane;

[0031] Step 6: The heading angle of the aircraft can be calculated by combining the angle ψ1 between the binocular camera baseline and the north direction, and the angle ψ2 between the horizontal projection of the line connecting the two reference points on the side of the aircraft and the image plane.

[0032] When the RTK binocular direction finding system is placed horizontally, the binocular camera baseline coincides with the RTK dual-antenna receiver direction finding baseline.

[0033] When the RTK binocular direction finding system is placed horizontally, the image planes of the two cameras are in a vertical plane.

[0034] The distance between the two RTK antennas of the RTK dual-antenna receiver is greater than 2 meters, and the distance between the two cameras is greater than 2 meters.

[0035] Among them, the distance between the two reference points is greater than 2 meters.

[0036] Wherein, the heading angle of the aircraft is ψ 1+ ψ2.

[0037] Example 1

[0038] In this embodiment, the two RTK receiver antennas and two cameras of the RTK binocular direction finding system are fixedly mounted at both ends of the instrument bracket; two special marks are set on the side of the aircraft as reference points; the line connecting the two reference points is parallel to the aircraft's roll axis; the two reference points appear simultaneously in the field of view of the two cameras; the two RTK antennas are used to measure the north angle of the binocular direction finding system baseline; the position of the reference points in the camera coordinate system is measured by the position of the reference points in the image planes of the two cameras; the heading angle of the line connecting the two reference points is calculated by combining the RTK direction finding results and the camera data;

[0039] The two RTK antennas and two cameras are fixedly mounted on an instrument bracket, and when the RTK binocular direction finding system is placed horizontally, the binocular camera baseline coincides with the RTK dual antenna direction finding baseline;

[0040] The two RTK antennas and the two cameras are fixedly mounted on an instrument bracket, and when the RTK binocular direction finding system is placed horizontally, the image planes of the two cameras are in a vertical plane;

[0041] The two RTK antennas and the two cameras are fixedly mounted on the instrument bracket, with the distance between the two RTK antennas being greater than 2 meters, and the distance between the two cameras being greater than 2 meters;

[0042] Two special marks are set on the side of the aircraft as reference points, and the distance between the two reference points is greater than 2 meters;

[0043] The two RTK antennas are used to measure the heading angle of the binocular direction finding system baseline, and the average value of the measurement data over a period of time is calculated.

[0044] Example 2

[0045] In this embodiment, the RTK binocular direction-finding system needs to be calibrated before determining the aircraft's heading vector. In step 1, the RTK binocular direction-finding system is calibrated so that when the RTK binocular direction-finding system is placed horizontally, the binocular camera baseline coincides with the RTK dual-antenna direction-finding baseline, and the binocular camera image plane is perpendicular to the horizontal plane.

[0046] In a preferred solution, the RTK antenna spacing and the binocular camera spacing are both greater than 2 meters.

[0047] A horizontal reference is required for field testing. In step 2, two reference points are selected on the side of the aircraft, with the line connecting them parallel to the aircraft's roll axis. Once the aircraft is ready for launch, place the tripod in a suitable location, adjust the tripod to a horizontal position, and place the RTK binocular direction-finding system horizontally on the tripod, ensuring that both reference points fall within the field of view of the binocular direction-finding system's two cameras.

[0048] In a preferred solution, the reference point can be selected as the intersection of the cross lines at the front and rear ends of the aircraft side. The line connecting the two reference points should be parallel to the roll axis of the aircraft, and the distance between them should be greater than 2 meters.

[0049] The angle between the binocular camera baseline and the north direction can be measured using an RTK receiver. In step 3, the RTK binocular direction-finding system is powered on, and the north angle output by the RTK receiver is continuously collected for a period of time. The sampled results are averaged and recorded as the angle ψ1 between the binocular camera baseline and the north direction.

[0050] The angle between the projection of the line connecting the reference points in the horizontal plane and the binocular baseline is measured by computer vision methods. Step 4 Obtain the coordinates of the two reference points in the camera coordinate system. Calculate the coordinates of the reference points in the camera coordinate system according to equations (1) to (6). The position of the reference point P1 in the binocular camera image plane is shown in Figure 2 .

[0051] The coordinates of point P1 in the camera coordinate system are:

[0052]

[0053]

[0054] Similarly, the coordinates of point P2 in the camera coordinate system are

[0055]

[0056] Step 5 Calculate the X coordinates of the two reference points in the camera coordinate system c O c Y c The angle ψ2 between the projection in the plane and the baseline.

[0057] ψ2=atan2(Y c2 -Y c1 X c2 -X c1 ) (7)

[0058] Calculate the heading of the aircraft. Step 6 The angle between the binocular camera baseline and the north direction and the two reference points in the camera coordinate system X c O c Y c The sum of the angles between the projection in the plane and the baseline is the heading angle

[0059] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for measuring aircraft heading based on RTK receiver and computer vision, characterized in that: The method is implemented based on an RTK binocular direction finding system, which includes a horizontally placed calibrated RTK dual-antenna receiver and a binocular vision direction finding system; The method comprises: Step 1: Calibrate the RTK binocular direction finding system. When the RTK binocular direction finding system is placed horizontally, the binocular camera baseline and the RTK dual-antenna direction finding baseline coincide, and the binocular camera image plane is perpendicular to the horizontal plane. Step 2: Select two reference points on the side of the aircraft, with the line connecting the reference points parallel to the aircraft's roll axis. After the aircraft is ready for launch, place the tripod at a suitable location at the launch point. Adjust the tripod to a horizontal position and place the RTK binocular direction finding system horizontally on the tripod so that both reference points fall within the field of view of the RTK binocular direction finding system's two cameras. Step 3: Power on the RTK binocular direction finding system, continuously collect the heading angle output by the RTK dual antenna receiver, and average the sampling results over a period of time. Calculate the average value and obtain the angle between the binocular camera baseline and the north direction, which is recorded as ψ 1 ; Step 4: Obtain the positions of the two reference points in the binocular camera image plane, and calculate the coordinate positions of the two reference points in the camera coordinate system based on the binocular vision positioning principle; Step 5: Based on the coordinate positions of the two reference points in the camera coordinate system, calculate the angle ψ between the projection of the line connecting the two reference points in the horizontal plane and the image plane 2 ; Step 6: Calculate the angle ψ between the binocular camera baseline and the north direction 1 , and the angle ψ between the projection of the line connecting the two reference points on the side of the aircraft in the horizontal plane and the image plane 2 , the heading angle of the aircraft can be calculated.

2. The method for measuring aircraft heading based on RTK receiver and computer vision according to claim 1, wherein: When the RTK binocular direction finding system is placed horizontally, the binocular camera baseline coincides with the RTK dual-antenna receiver direction finding baseline.

3. The method for measuring aircraft heading based on RTK receiver and computer vision according to claim 1, wherein: When the RTK binocular direction finding system is placed horizontally, the image planes of the two cameras are in a vertical plane.

4. The method for measuring aircraft heading based on RTK receiver and computer vision according to claim 1, wherein: The distance between the two RTK antennas of the RTK dual-antenna receiver is greater than 2 meters, and the distance between the two cameras is greater than 2 meters.

5. The method for measuring aircraft heading based on RTK receiver and computer vision according to claim 1, wherein: The distance between the two reference points is greater than 2 meters.

6. The method for measuring aircraft heading based on RTK receiver and computer vision according to claim 1, wherein: The heading angle of the aircraft is ψ 1 + ψ 2 .

7. The method for measuring aircraft heading based on RTK receiver and computer vision according to claim 1, wherein: The method belongs to the technical field of aircraft state acquisition.

8. The method for measuring aircraft heading based on RTK receiver and computer vision according to claim 1, wherein: The method can be applied to the rapid measurement of heading under field conditions.

9. The method for measuring aircraft heading based on RTK receiver and computer vision according to claim 1, wherein: The method uses an RTK receiver to establish a north reference, and uses binocular vision to measure the angle between the line connecting two reference points on the side of the aircraft and the north direction, thereby achieving the measurement of the aircraft's heading angle.

10. The method for measuring aircraft heading based on RTK receiver and computer vision according to claim 1, wherein: The method has a simple algorithm and is easy to implement in engineering, and has great potential for engineering promotion and application.

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